1. Field of Invention
This invention relates to a system for oral delivery of gases pressurized above ambient, and in particular, to a system, including a novel mouthpiece, for the oral delivery of air in continuous positive airway pressure (CPAP) treatments of sleeping disorders such as sleep apnea.
2. Description of the Prior Art
Sleep apnea treatments have been significantly advanced with the introduction of continuous positive airway pressure (CPAP) treatments. These treatments, as introduced, involve the supply of gases from a gases supply or blower to a patient through a conduit and nasal mask to provide an elevated internal pressure in the users airways to assist the muscles to keep the airways open. This airstream is provided to the user through a nasal mask applied over the nose and held in place by a harness. This configuration has been almost universally adopted based on the well known observation that humans show a decided preference for nasal breathing during sleep. For this reason, little development has been undertaken into other possible methods of providing the pressurized airstream to a user.
Oral delivery is suggested in EP 818, 213, which shows an apparatus for oral delivery of air in a CPAP treatment. The apparatus includes a mouthpiece adapted to fit inside the mouth between the roof of the mouth, the hard palate, and the tongue, and having a periphery which can be gripped between the teeth. It is thought by the applicants that this is significantly more intrusive than is necessary and is liable to movement and consequent discomfort (although not outright removal) under the relaxation of sleep. It has the additional disadvantage that with the user fully relaxed, such as in the case of sleep, a distension in the user's jaw and subsequent opening of the mouth can reduce the sealing effectiveness of the mouthpiece and reduce the efficacy of the CPAP treatment.
Because the mouthpiece in EP 818,213 is gripped between the user's teeth, a further disadvantage results in that the mouthpiece requires custom orthodontic fitting to ensure that the mouthpiece matches the user's mouth and teeth layout. Custom orthodontic fitting is time consuming and removes the capability of effective mass manufacture. Consequently, the mouthpiece in EP 818,213 is expensive, creating a significant barrier to the patient adoption of the device.
A similar gases delivery mouthpiece, for use with a respirator, is shown in WO 90/03199. WO 90/03199 discloses an orthodontic device which is adapted to be gripped between the jaws of a user and to accommodate the user's teeth within a series of upper and lower cavities. A base member of the mouthpiece is shaped and fits against the hard palate of the user. This mouthpiece again has the disadvantage of requiring custom orthodontic fitting. Furthermore, as a result of the mouthpiece's substantial thickness and size, the mouthpiece is substantially rigid in the vestibule regions of the mouth. The mouthpiece is clamped in place by an outer shield which engages the outside of the user's lips.
A paper by E Veres entitled “Clinical trial of an oral vestibular shield for the control of snoring” (Journal of the Dental Association of South Africa, January 1993) describes the use of a shield intended to be retained in the vestibule of the mouth to seal the mouth and to promote nasal breathing which has been conventionally considered to be more beneficial than oral breathing. Humidified CPAP treatments delivered orally, however, actually derive greater benefit than those delivered nasally because secondary leakage through the nasal passages during oral delivery is significantly less than oral leakage during nasal delivery. The shield depicted in the paper is formed from flexible ethylene vinyl. The shield is custom trimmed and is custom fitted by heating to a malleable temperature and deformed by applied pressure.
Other possible mouthpiece designs are shown for example by use in self contained underwater breathing apparatus systems, for example as depicted in U.S. Pat. No. 4,862,909. This mouthpiece is a mouth guard type and is clamped between the teeth. A flange extends both in front of and behind the teeth.
Prior art mouthpieces are not well adapted for use in CPAP treatments because they are intended for conscious gripping by the user, and have been found subject to accidental removal with a user in a completely relaxed state such as sleep. The present invention overcomes this problem and present several other advantages which will become apparent upon a reading of the attached specification, in combination with a study of the drawings.